added usage printing
added usage printing

johnnyliu27/openmc,shikhar413/openmc,amandalund/openmc,mit-crpg/openmc,paulromano/openmc,samuelshaner/openmc,amandalund/openmc,wbinventor/openmc,johnnyliu27/openmc,liangjg/openmc,nhorelik/openmc,smharper/openmc,lilulu/openmc,amandalund/openmc,shenqicang/openmc,walshjon/openmc,johnnyliu27/openmc,wbinventor/openmc,paulromano/openmc,mjlong/openmc,lilulu/openmc,paulromano/openmc,shikhar413/openmc,shenqicang/openmc,smharper/openmc,kellyrowland/openmc,shikhar413/openmc,lilulu/openmc,liangjg/openmc,shikhar413/openmc,nhorelik/openmc,walshjon/openmc,smharper/openmc,liangjg/openmc,sxds/opemmc,johnnyliu27/openmc,paulromano/openmc,walshjon/openmc,smharper/openmc,mit-crpg/openmc,liangjg/openmc,kellyrowland/openmc,wbinventor/openmc,mit-crpg/openmc,samuelshaner/openmc,mjlong/openmc,amandalund/openmc,bhermanmit/openmc,mit-crpg/openmc,wbinventor/openmc,bhermanmit/openmc,samuelshaner/openmc,walshjon/openmc,samuelshaner/openmc,sxds/opemmc